Hybrid software-defined networking (SDN) and hybrid networks present a number of challenges. Challenges arise when planning hybrid SDN and legacy networks, including but not limited to, deploying new protocols, implementing rapid, error-free configuration, maintaining a highly skilled workforce, and managing merged control and data planes.
Although the implementation of a pure SDN network simplifies the network itself, this implementation is not only not always an option, it is also uniquely challenging. A pure SDN solution uses switches that are limited to simple tasks like forwarding. Additionally, SDN networks program all control functionality in a central controller and use an out-of-band network between the controller and switches. Because of these limitations, programming is difficult, it is unclear how to scale centralized control, there is no encryption (SDN has no encryption), and the necessity of an out-of-band network adds complexity to the data plane.